Dual disconnect drive assembly

ABSTRACT

A dual disconnect differential assembly for four-wheel drive (4WD) vehicle is disclosed. This disconnect differential assembly connects/disconnects both output shafts of a differential assembly simultaneously from the respective universal joints of the drive assembly. Both output shafts are interconnected to provide simultaneous sliding along an axial direction. A clutch mechanism associated with the inboard side of each universal joint (which may be a constant velocity joint) and with the output shafts is provided for simultaneous connection and simultaneous disconnection of the output shafts from the outboard side of the universal joint. The dual disconnect differential assembly herein is simple, compact, and reliable. It overcomes the disadvantages associated with single axle disconnect mechanisms presently in use. It also provides a simpler, more compact, and more reliable dual disconnect differential mechanism than any such mechanism presently known.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] This invention relates to differential disconnect driveassemblies or mechanisms, and in particular to dual disconnect driveassemblies, for four-wheel drive vehicles which can be operated ineither a two-wheel drive mode or a four-wheel drive mode.

[0003] 2. Description of Related Art

[0004] Four-wheel drive vehicles, which are operable in either atwo-wheel drive mode or a four-wheel drive mode, have gained widespreadpopularity. Axle disconnect mechanisms, or differential disconnectmechanisms or assemblies for such vehicles are known.

[0005] Commonly used disconnect mechanisms for four-wheel drive vehiclesdisconnect only one of the two output shafts on an axle assembly whichis driven part time. This causes the pinion gears and the side gears ofthe differential to rotate due to back driving, although thedifferential case remains stationary. This is not compatible withspeed-sensitive limited slip differentials. Also, single axle disconnectmechanisms may cause noise and wear and poor fuel economy due torotation of the differential components while the vehicle is intwo-wheel drive mode.

[0006] Various dual disconnect differential assemblies or mechanismshave been proposed. These mechanisms in general have an unnecessarynumber of moving parts, are fairly complex, and would be suitable onlyfor installation on relatively wide vehicles because of the spacerequired. Earlier designs have interposed a clutch member between theside gear and the output shaft. None has achieved desirable commercialacceptance.

SUMMARY OF THE INVENTION

[0007] This invention comprises a differential having first and secondside gears, which are rotatable about a common transverse axis.Rotatable first and second output shafts are co-axial with the sidegears and are arranged to drive a pair of respective wheels, and auniversal joint (e.g., a constant velocity joint) is disposed betweeneach output shaft and a respective wheel end. In accordance with thisinvention, a clutch mechanism is used for placing each output shaftsimultaneously into or simultaneously out of driving engagement with theinboard side of an associated universal joint. An actuator is used toslidably and concurrently move the output shafts between the clutchengaging position and the clutch disengaging position with respect tothe universal joint to thereby disconnect the output shaft from theassociated axle shafts and joint assembly.

[0008] In the preferred embodiment, the output shafts have clutchmembers for engaging the clutch members of the respective first andsecond universal joints, with the output shafts being simultaneouslyslidable in a first direction to a clutch engaging position andsimultaneously slidable in a second direction to a clutch disengagingposition. The output shafts are interconnected to provide simultaneoussliding movement.

[0009] A preferred dual disconnect differential assembly according tothe invention includes, as axially engageable clutch members, a splineinterface connection between the first and second universal joints andthe respective first and second output shafts. A biasing means isprovided for biasing the output shafts to a clutch disengaging position.The vehicle is in two-wheel drive mode when the clutch is disengaged andin four-wheel drive mode when the clutch is engaged. An actuator causessliding movement of the interconnected output shafts to translate theshafts into the disengaged position.

[0010] Another aspect of the clutch mechanism of the invention providesa pair of split-spline teeth on both the output shafts and therespective universal joints to reduce the travel distance required toengage/disengage the dual axle disconnect system.

[0011] The differential assembly of the present invention possessesseveral advantages, including greater fuel economy, less wear, and lessnoise compared to previously known disconnect mechanism in which only asingle output shaft and its axle shaft are disengaged from drivingengagement with a differential when two-wheel drive mode is selected.Advantages of the present invention compared to previously known dualdisconnect differential assemblies include a more robust design withoutincreased packaged size, fewer parts and greater compactness, whichmakes it possible to utilize the present dual disconnect drive mechanismon any size vehicle, including a sub-compact automobile. This makes itpossible to offer four-wheel drive on smaller vehicles, includingsub-compact automobiles, which have not previously had optionalfour-wheel drive because of the space requirements of presently knowndual disconnect mechanism.

BRIEF DESCRIPTION OF THE DRAWINGS

[0012]FIG. 1 is a sectional plan view of the invention according to apreferred embodiment of the invention.

[0013]FIG. 2 is an enlarged sectional plan view of the inventionaccording to a preferred embodiment of FIG. 1.

[0014]FIG. 3 is a partial sectional plan view according to the inventionaccording to a second embodiment of the invention. In this embodiment,the return spring 42 is not required.

[0015]FIG. 4 is a perspective view of the interconnecting collarconnecting the two output shafts of the second embodiment.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016] This invention will now be described in detail with reference tothe best mode and preferred embodiments thereof.

[0017] Referring now to FIG. 1, a dual disconnect differential assembly(or mechanism) according to this invention is shown for a front axle ofa four-wheel drive (4WD) vehicle having a full-time rear axle and apart-time front axle.

[0018] The differential assembly in general is driven by alongitudinally extending pinion shaft (or input shaft) not shown, whichin turn may be driven by a drive shaft (not shown) which extendslongitudinally from a vehicle transmission. The pinion shaft may engagea ring gear (not shown), which is affixed (e.g., bolted) to adifferential case 12. Differential case 12 is rotatably mounted in adifferential housing 14 by means of bearings 15. Differential case 12and the ring gear affixed thereto rotate about a transverse horizontalaxis ‘x-x’, which is the axis of output shafts 24, 25.

[0019] The differential used in the practice of this invention mayfurther include a differential cross pin 16, and pinion gears 18 whichare rotatably mounted with respect to cross pin 16. The differentialfurther includes first (or left-hand) and second (or right-hand) sidegears 20 and 21, respectively (see FIGS. 1, 2, and 3). Side gears 20 and21 are coaxial and rotate about a common transverse axis, which is alsothe common axis of the aforementioned output shafts 24, 25.

[0020] The outboard ends of the output shafts 24, 25 are provided withuniversal joints 50, 60 (e.g. constant velocity joints) between theoutput shafts 24, 25 and the respective wheel ends.

[0021] In accordance with the present invention, a clutch mechanism isprovided between the universal joints 50, 60 have respective outputshafts 25, 24 in the form of splines (for example, splines 25 a, 50 a),as best seen in FIG. 2. These splines are formed on central bores ofrespective inner members at the inboard side of each universal joint 50,60.

[0022] As with the conventional differential drive assembly, the dualdisconnect axle assembly 14 of this invention includes a coaxial first(or left-hand) output shaft 24 and a second (or right-hand) output shaft25. These output shafts 24, 25 extend transversely and are coaxial withside gears 20, 21. These output shafts 24, 25 extend from inboard endsnear cross pin 16 to outboard ends, which extend outside thedifferential housing. Splines (e.g. splines 25 a, 50 a) are provided atthe inboard ends of universal joints 50, 60 for selectively driving thesame and which may be conventional (e.g., universal joints) provided atrespective outboard ends of output shafts 24, 25 and extend transverselyoutwardly to wheels (not shown) at the sides of the vehicle.

[0023] According to one important aspect of this invention, the firstand second output shafts 24, 25 are interconnected and axially slidabletogether as a unit. In other words, the present invention preferablyprovides a linking member 29 in the form of a linking rod or othersuitable member that extends through the differential assembly toconnect the two output shafts 24, 25. With this arrangement, theinvention provides simultaneous axial movement of the output shafts tothereby mutually disconnect the first and second output shafts 24, 25from the first and second universal joints 50, 60. In the embodiment ofFIG. 1, the linking rod 29 passes through the cross pin 16. In thealternate embodiment of FIG. 3, the linking member 129 takes the form ofa connecting sleeve that connects the output shafts 24, 25. In thearrangement of FIG. 3, the cross pin 16 passes through the connectingsleeve 129 at apertures 130. In both illustrated designs, the two drivenoutput shafts 24, 25 are securely linked together to provide mutuallinear sliding movement between the clutch engaged and disengagedpositions.

[0024] The dual disconnect axle assembly 14 of this invention includes aclutch mechanism for simultaneously placing output shafts 24, 25 eitherinto or out of driving engagement with respective universal joints 50,60. The splines between respective output shafts and the universaljoints form part of this clutch assembly or mechanism.

[0025] The entire set of clutch members, including internally-splinedinner member 50 of the universal joints and externally-splined outputshafts 24, 25, are shown in clutch disengaging position in FIG. 1, beingthe normal position. Upon actuation, as will be described subsequently,the axially slidable output shafts 24, 25 slide to the left as seen inFIG. 1 into a clutch engaging position, in which clutch members orsplines on respective universal joints 50, 60 are in engagement withrespective splines on respective output shafts 24, 25. Output shafts 24,25 rotate with respective universal joints 50, 60 when the clutchmechanism is in the clutch engaging position, and rotate independentlyof the respective universal joints 50, 60 when the clutch mechanism isin the clutch disengaging position.

[0026] A compression spring 42 serves as biasing means to urge theaxially slidable output shafts 24, 25 to clutch disengaging position,i.e., to the right as seen in FIG. 1. Spring 42 abuts the first orleft-hand output shaft 24.

[0027] To actuate the clutch mechanism, a clutch actuator 40 may beprovided as a shift fork having a bifurcated end portion which isreceived in groove 38 of clutch collar 36 fixedly provides on one of theoutput shafts. The shift fork 40 may be actuated by known means 41,e.g., by electrical (which is preferred) or by hydraulic, pneumatic,vacuum, or mechanical means. Actuation may be initiated eitherautomatically or by a manual operator, such as a manual or pedal controlin the vehicle cab.

[0028] The output shafts 24, 25 and collar 36 are normally in clutchdisengaging position, i.e., to the right as seen in FIG. 1. The vehicleis in two-wheel drive (2WD) mode when the clutch is disengaged. Toengage the clutch mechanism and place the vehicle in four-wheel drive(4WD) mode, clutch actuator 40 moves clutch collar 36 to the left asseen in FIG. 1 against the bias of compression spring 42. Clutch collar36 pushes the output shafts 24, 25 to the left against the bias ofspring 42, thereby placing the clutch members or splines on respectivedriven output shafts 24, 25 in engagement with respective clutch membersor splines (e.g., splines 52 a) on respective universal joints 50, 60.With the clutch mechanism thus engaged, the output shafts 24, 25 areconstrained to rotate at the same speeds as respective universal joints50, 60 and power is transmitted to the respective wheel ends (not shown)through the joints 50, 60. When the need for four-wheel drive no longerexists, clutch actuator 40 is moved to the right. This also slidesclutch collar 36 to the right. Compression spring 42 then pushes outputshafts 24, 25 to the right, i.e., to the clutch disengaging position, toreturn the vehicle to two-wheel drive mode.

[0029] The drawings herein show a differential assembly for a front axleof a vehicle. Most current vehicles which have four-wheel drive have afull-time rear axle and a part-time front axle. However, some recentfour-wheel drive vehicles have a full-time front axle and a part-timerear axle. The differential assembly of this invention can be used oneither the front axle or the rear axle, whichever axle is the part-timeaxle.

[0030] The compression spring 42 (or other biasing means) is normallybiased toward the clutch disengaging position, which results indisengagement of the part-time axle, since it is normally preferred tooperate in two-wheel drive mode with the part-time axle disengagedexcept when driving conditions call for four-wheel drive operation.However, this spring can be biased toward clutch engaging position ifdesired. Other biasing means, as for example, an air spring, can be usedin place of the compression spring shown if desired.

[0031] Further, the biasing means can be dispensed with entirelyprovided that some means, such as magnets on the relatively slidablemembers. Such magnets, if used, must not be so strong as to prevent orimpede relative rotation between adjacent axially slidable members.Other mechanical mechanisms which function to shift the output shafts24, 25 to the clutch disengaging position are also contemplated herein,and the second embodiment shown in FIG. 3.

[0032] It is possible to use a solenoid operator, e.g., an annularsolenoid operator surrounding the output shafts 24, and, in that case,to dispense with collar 36 if desired. However, the illustratedapparatus, including a collar 36 and a shift fork 40, is preferred sincethis gives more versatility both as to type and location of theactuator.

[0033] It is also possible to use a spider (which typically including aring at its center with a plurality of radially extending arms extendingoutwardly from the ring) in place of the cross pin 16 if desired.

[0034] The present invention provides a simple and reliable mechanismfor simultaneous differential connect and simultaneous differentialdisconnect. In other words, both output shafts 24, 25 are simultaneouslyconnected or disconnected from their respective universal joints 50, 60in the apparatus of this invention. The novel dual disconnectdifferential assembly herein avoids the known disadvantages of singleshaft disconnect mechanism, such as back drive, as has been discussedearlier.

[0035] The dual disconnect differential assembly of this invention isalso compact. This makes part-time, dual disconnect four-wheel drive forcompact and sub-compact vehicles possible.

[0036] While this invention has been described in detail with referenceto the preferred embodiments thereof, it shall be understood thatvarious modifications (including those specifically discussed above andothers) can be made without departing from the scope and spirit of thisinvention.

What is claimed is:
 1. A dual disconnect drive axle assembly for anautomotive vehicle, said assembly comprises: first and second coaxiallyaligned output shafts driven by first and second side gears of adifferential assembly; first and second universal joints adapted torespectively transmit torque from said first and second output shafts;wherein said first and second output shafts are axially slidable tothereby disconnect said first and second output shafts from said firstand second universal joints.
 2. The dual disconnect differentialassembly according to claim 1, further comprising a interconnectingmember interconnecting said first and second output shafts to translatein simultaneously along said transverse axis, wherein said first andsecond output shafts are axially slidable and interconnected to providesimultaneous axial movement of said output shafts.
 3. The dualdisconnect differential assembly according to claim 1, wherein saidinterconnecting member comprises a rod extending from an inboard end ofsaid first output shaft to an inboard end of said second output shaft.4. The dual disconnect differential assembly according to claim 3,wherein said rod passes through said cross pin.
 5. The dual disconnectdifferential assembly according to claim 2, wherein said interconnectingmember comprises an interconnecting collar adapted to receive said crosspin passing therethrough, said interconnecting collar extending betweenand connecting said first and second output shafts.
 6. The dualdisconnect differential assembly according to claim 1, furthercomprising: first clutch members on said first and second universaljoints; and second clutch members on said first and second output shaftsfor engaging said first clutch members of respective first and seconduniversal joints.
 7. The dual disconnect differential assembly accordingto claim 1, further including a ring which is mounted on one of saidfirst and second output shafts for axially moving said first and secondoutput shafts simultaneously in the same direction between a clutchengaging position and a clutch disengaging position.
 8. The dualdisconnect differential assembly according to claim 7, further includingan actuator, wherein said actuator includes an arm for engaging saidring for slidably moving said first and second output shafts betweensaid clutch engaging position and said clutch disengaging position. 9.The dual disconnect differential assembly according to claim 1, whereinouter surfaces of said first and second output shafts and inner surfacesof said first and second universal joints have complementary splines.10. The dual disconnect differential assembly according to claim 1,wherein an inner member of said first and second universal joints haveaxially extending central bores, said first clutch members on said firstand second universal joints are splines formed on respective portions ofsaid bores, said second clutch members on said first and second outputshafts are splines formed on outer surfaces thereof, the splines on saidfirst and second universal joints and the splines on said first andsecond output shafts being in engagement when said first and secondoutput shafts are in a clutch engaging position and out of engagementwhen said first and second output shafts are in a clutch disengagingposition.
 11. The dual disconnect differential assembly according toclaim 10, wherein a compression spring urges said first and secondoutput shafts toward one of said clutch engaging position and saidclutch disengaging position.
 12. The dual disconnect differentialassembly according to claim 11, wherein said compression spring urge ssaid first and second output shafts toward said clutch disengagingposition.
 13. The dual disconnect differential assembly according toclaim 1, wherein said first and second output shafts are in drivingengagement with an inboard side of said first and second universaljoints when said first and second output shafts are in a clutch engagingposition and are in a free-wheeling mode when said first and secondoutput shafts are in a clutch disengaging position.
 14. The dualdisconnect differential assembly according to claim 13, wherein saidfirst and second output shafts and said first and second universaljoints are capable of rotation at different speeds in both driven modeand free-wheeling mode of said first and second output shafts.
 15. Thedual disconnect differential assembly according to claim 1, furthercomprising a splined interconnection between the output shafts and theuniversal joints whereby splines of the splined interconnection aredivided into a pair of axial-spaced rows of gear teeth on each of saidfirst and second output shafts and said first and second universaljoints.
 16. A method of changing between two-wheel drive to four wheeldrive modes for a four-wheel drive (4WD) vehicle, comprising the stepsof: providing a clutch mechanism between first and second output shaftsextending from opposite ends of a differential assembly and first andsecond universal joints respectively driven by said first and secondoutput shafts sliding said first and second output shafts along an axialdirection to disconnect said output shafts from said first and seconduniversal joints.
 17. The method of claim 16, further comprising thestep of providing a splined interconnection between the output shaftsand the universal joints whereby the splines are divided into a pair ofaxial-spaced rows of gear teeth.
 18. The method of claim 16, whereinsaid output shafts are interconnected to simultaneously translate duringsaid step of sliding.